Monday SpaceX Launch Preps Continue

International Space Station Program officials and representatives of SpaceX decided Saturday to continue preparations for the launch of the Falcon 9 rocket and the Dragon cargo craft to the space station Monday from Launch Complex 40 at the Cape Canaveral Air Force Station, Fla., despite the failure Friday of a backup computer component that provides redundancy for commanding the Mobile Transporter rail car on the truss of the station. A final decision on whether to launch Dragon Monday will not be made until another status meeting is conducted Sunday morning.

The component, called a multiplexer demultiplexer (MDM) is one of more than a dozen housed on the truss of the station that routes computer commands to various systems on the outpost. The failure Friday to a box called EXT-2, a backup box to a prime component in the S0 truss that measures 10.5 x 14.9 x 16.4 inches and weighs 50.8 pounds, occurred during a routine health check of the device.

The SpaceX Dragon commercial cargo craft was in the the grips of the Canadarm2 before being released May 31, 2012 during Expedition 31.

The prime multiplexer continues to operate flawlessly, and there has been no impact to station operations. The crew was informed of the problem and is in no danger, continuing its normal complement of research work and routine maintenance. A reboost of the station using the ISS Progress 53 thrusters was conducted Saturday as planned and placed the laboratory at the correct altitude for Soyuz crew landing and launch operations in May.

Station program officials, flight controllers and teams of engineers are working to determine whether there is any risk to launching the SpaceX cargo craft Monday. They will evaluate whether the station has enough redundancy to permit the launch to proceed, which would result in Dragon arriving at the station Wednesday where it will be grappled and berthed to the Earth-facing port of the Harmony module by Expedition Commander Koichi Wakata of the Japan Aerospace Exploration Agency and NASA Flight Engineer Rick Mastracchio. The station’s Canadarm2 robotic arm that would be used to capture and berth Dragon has other redundancy capabilities not affected by the backup MDM failure.

While a final decision on the SpaceX launch is being reviewed, another team of engineers is laying out a timeline for a contingency spacewalk that is required to replace the failed spare MDM. No date for the spacewalk has been scheduled. Such a spacewalk is one of the so-called “Big 12” spacewalks that station crews train to execute for the loss of a critical component on the complex.